H.A.L.'s one-point impression!!

- Insanity of the SPEC RPA-MG1

(Dec 5, 2019)

What is an insane amplifier that makes insane speakers sound amazing?

There's a reason why I start off with a series of insanities, contrary to the rhetoric in some magazine articles.

First of all, please take a look at the system configuration below to see what an insane speaker is.


It refers to Y'Acoustic System Ta.Qu.To-Zero, but please check the link below to see what I mean by the uncompromising pursuit of ideals while ignoring marketing-conscious design and manufacturing methods.

H.A.L.'s Hidden Story!! - Y'Acoustic System Ta.Qu.To-Zero


As a continuation of the above, no other speaker manufacturer in the world uses such parts in their crossover network. The rest of the hidden story must be told first!!


The extravagant and insane speaker, the Y'Acoustic System Ta.Qu.To-Zero, began to sound completely different from anything I had ever heard before, and that surprise and excitement motivated me.

That insane amplifier is the SPEC RPA-MG1!!


So, then, what made me say it is insane!?

I have been involved in the audio industry for a long time, and have pursued sound quality and conducted research at the Hi-End Audio Laboratory. Naturally, there are some subjective statements in this history, but they are my own theories based on what I have verified here and can be proven as the reproduced sound.

So, what was it about the SPEC RPA-MG1 that caught my attention?  I think I should start with that. Please refer to the following documents.

SPEC RPA-MG1000 (English document for overseas)


I call this amplifier insane, which means I have my own criteria for my judgement, and  it is consistent with each of the points I have been making in the following essay. I have held the same standards for 26 years now.

Most of the domestic components in the 1970s and 1980s had round, flat feet that touched the rack, and few of them used spikes. In that period, however, many overseas products were already on the market, with both speakers and components equipped with spiked feet.

As I mentioned in the essay above, I believe that the concept of mechanical grounding [mechanical earth] originated from GOLDMUND.
Of course, the concept of mechanical grounding requires that the housing of the components themselves has high rigidity and high mass. Later, Jeff Rowland carved a lump of aluminum to make the body of an amplifier, and although the methods differ, the pursuit of sound quality by increasing rigidity has become a common practice in high-end amplifiers.

Let's take this another way. Fundamentally, source components and speakers are transducers.

A tape deck converts magnetic signals into electrical signals, an FM tuner converts radio waves into electrical signals, a pickup cartridge converts mechanical signals into electrical signals, and a CD player converts optical signals into electrical signals. Speakers use these electrical signals and convert them into sound waves as mechanical actions.

This conversion to a different signal form is physically dependent on the subjectivity of the ideal sought by the designer in the comparison before and after the conversion.
In other words, when magnetic fields, radio waves, mechanical motions, and light are converted into electrical signals, it is almost impossible to analyze the error in the waveform and energy with respect to the fidelity between the original signal and the converted signal, strictly speaking. The same may be said of speakers.

As a typical example, the sound quality of analog players can be dichotomized according to whether or not they have a floating suspension mechanism, or in the case of Kiso Acoustic speakers, there is a method of consciously making the enclosure resonate as a second sound source, like a musical instrument. As a result, the individuality of the transducer is acceptable  because it is selected according to user preferences. Therefore, audio products can only be evaluated and discussed in terms of their resulting sound quality.

However, the amplifier is the only part of the audio system that uses electrical signals for both input and output! This means that the input and output signals can be analyzed and evaluated, using electrical measuring instruments. There is a firm standard that input and output waveforms must not be altered in any way by the subjective taste or intentions of the designer. At the same time, it should be acknowledged that sound quality cannot be described by waveform observation alone.

Now, let’s start from where we left off. What was it about the SPEC RPA-MG1 that caught my attention?

I have a negative opinion about the expression, "An amplifier is a musical instrument.” on the SPEC website and in the Japanese documentation.

All musical instruments are composed of a vibrating sound source and a resonating body, which is the string, the tube, or the percussion instrument itself. And most of them have a resonant wooden or metal body. The vibrations of the sound source are not resonated by a mechanical linkage, but by the sound waves emitted by the source.

A musical instrument resonates through compressed waves of air. Kiso Acoustic, which I mentioned earlier, is the best example. However, I don't believe in the concept of the amplifier itself creating resonance through sound pressure.

One part of the document says, "It vibrates along with the musical signal, producing a beautiful tone." As mentioned above, this is completely contrary to the design philosophy of the amplifier, which is high rigidity and high mass, and to eliminate the harmful elements of sound pressure and mechanical vibration by mechanical grounding. The amplifier is not a transducer.

I disagree with SPEC's expression,"Musical expression is tone.”

I don’t deny that the mainstay of tonal expression is the microsignals that make up the complex overtones, but overtones are contained in the signal output by the source component, the transducer. This runs counter to high fidelity, if the amplifier is creating them in a staged manner.

That is acceptable in terms of faithfully delivering the overtones contained in the input signal to the speaker, but this is because it is considered to add something that is not in the input signal. This is in terms of creating the resonance mentioned above as a means of doing so.

What do you expect from a speaker cable?

In the audio world, Hi-Fi is an acronym for High Fidelity, which refers to the high fidelity of the entire playback system in comparison to the original sound. The following adage has been passed down from generation to generation.

"Add nothing, subtract nothing."

This is an importanti factor that is required for the performance of speakers and components. Naturally, the same philosophy is required for various cables. However, what kind of sound is the original sound, and what is the standard for "adding nothing and subtracting nothing"?

The most important role of an amplifier, which is not a transducer, is to "pull nothing". This is the most important role that an amplifier plays as a Hi-Fi component for both the source and the speakers. This is why it has long been said that an amplifier is a cable with gain. From this point of view, I can only think that SPEC's method of using wood as a component of the amplifier is "adding something". If it is the echoes of music, then it is adding something that is not in the original source signal.

If an amplifier adds resonance to a sound that was not included in the recording in the first place, it is a distortion of the original signal. In a concert hall recording, it is difficult to distinguish when an amplifier adds to the resonance of a huge space. However, I can’t help but think from experience that this can obscure the clear musical sounds of a precisely-controlled studio recording, resulting in a lack of focus and the imposition of certain tones.

I don't deny the application of the PWM method as seen in the English document of the SPEC RPA-MG1 in terms of electronic technology as hardware, and the insistence on using high performance components for each item, but the SPEC RPA-MG1 goes against common sense when it comes to the fundamental design concept of an amplifier!

"Tight bass," "delicate sharpness," "wide range and keen response," "neat and cool sound," "hard contours," "fine detail," "sharp focus," "a tendency to sharply cut off unnecessary swelling," "sharp and instantaneous rise to splendor.
Looking back at audio magazines from five years ago, I found that many of these expressions were used to describe Goldmund. There are many more expressions, which I am not adding here, but I think they are sufficient in terms of common nuances and are well applied as expressions.

The nuances of these words can then be compared and contrasted as follows.

★.1 "sharp rather than obtuse," "hard rather than soft," "cool rather than hot," "precise rather than vague," "tight rather than loose," "hard material rather than soft material.
I think many people have this kind of impression, and they are not wrong.

However, I understand these expressions with one additional condition. At least in the field of electronics, such as amplifiers including D/A converters, I don't think these expressions are wrong.

★.2 In other words, it is a group of devices where electrical signals are input and electrical signals are output.

"A speaker that converts electrical signals into mechanical vibrations, a CD transport that converts optical signals into electrical signals.”
All of these devices, including the so-called transducers, are based on Goldmund's philosophy, and I realized that there is an exquisite balance of musical textures that can only be experienced by listening to them in unison.

There are many brands that have gained recognition by producing only amplifiers, speakers, or other products in specific genres, but there are few that have truly built up their products from start to finish, based on their own principles, valuing their high-end status.

As one of the few people who was able to listen to their unified system, I can't help but feel a sense of mission to pass on the correct recognition and understanding of Goldmund to the music lovers in Japan.

New common sense comes into being through listening to the insane SPEC RPA-MG1!!

It is now well known that classical music pieces, especially orchestral pieces in concert halls, often have reverberation applied when they are mastered in the studio.

It is not unreasonable for the listener to think that the echoes of famous concert halls around the world are included in the recording, and that this reverberation is the beautiful sound of those halls. However, in reality, the sound quality is often manipulated to add resonance so that the music can be comfortably enjoyed as a product.

Then, in order to analyze the individuality of the amplifier from the expressions in ★.1 quoted above, I considered whether or not the selection of a hall recording would be preferable from the start. If the amplifier has the characteristic of adding resonance, as mentioned above, it might be perceived as a hall echo, and it would be difficult to judge whether it is staged by the amplifier or not.

When playing music produced and recorded in a huge concert hall, many people will feel positive about the added reverberation, even if it is not part of the recorded signal.

I started listening to Taeko Onuki/ATTRACTION "Four Seasons," which is one of the studio recordings that I can't ignore, to verify the clear sound of my assigned piece…


The intro to this song begins with Hirokazu Ogura's guitar and Kenji Takamizu's wood bass, both of which are not localized on the axis of the speakers. The guitar is located midway to the left of the center, and the bass midway to the right of the center, in a space where there is actually no sound source to begin with.

The intro for both of them comes about 10 to 11 seconds later, followed by the triangle in the center, and Taeko Onuki's vocals 12 seconds later.

"What? This guitar sounds completely different! I've never heard this kind of musical tone before! Why does the bass sound so different?

In just ten seconds, I was captivated! The musical texture of the acoustic guitar was completely different from anything I had heard before, and this was confirmed by the wood bass as well.  My thought process was literally occupied with a desperate feeling of pursuit for the reason.

This piece is 20-years old and I have listened to it countless times on many speakers and sound systems in my listening sessions.

If the SPEC RPA-MG1 is bringing about the sound quality that can be heard here now, I can't help but think that the sound I've been hearing and the direction I've been pursuing was in the direction of ★.1!  That doesn't mean it was wrong. It's not a debate about which is right, because they are different!

Think of a silk scarf from an upscale name-brand. Whether you tie it or wrap it around yourself, the lustrous fabric with its colorful prints will come loose effortlessly without any resistance when you try to untie it, and it will retain its original luster without leaving a single crease.
When you try to pull out the scarf by lightly grasping it, you feel not even the slightest friction and it slips easily between your fingers without any sound. You sigh at the divine smoothness that can be felt on the skin. However, there is no warmth in the extremely thinly woven silk, and the moment it touches your skin, you will feel a chill that will give you an image of the delicacy of the woven yarn.

And, here is the most important thing. Let's say you wrap something in a scarf.
Even if you just drape it softly over the object, you can still see the outline of the contents, which can be either pointy or round. If you were to literally wrap it, the thin fabric would show the shape of the contents as clearly as wrapping paper. This is the visual representation of ★.1.

However, the musical texture you hear with the SPEC RPA-MG1 is different! It's like an Imabari towel!


There are many different types of loop pile woven towels, but Imabari towels are synonymous with high quality towels. The touch of the towel is incredibly soft, highly absorbent, and delicate. In addition, it does not feel chilly to the touch, and you may want to use it as a scarf. The warmth and subtle temperature feeling is absolutely comfortable!

The finely woven pile fabric is very flexible, so it fits perfectly when you wrap it around something, and when you lightly grip it and pull it out, it slips through your fingers leaving a soft and fluffy feeling.

However, when you place a delicately airy towel on your open hand, it clearly shows the tips of your fingers, but I think it has a kind of enveloping quality, as it curves sensually in a soft and natural drape, hiding the sharp sides of its contents.

I have been struggling to understand and explain what SPEC is aiming for, how it differs from the direction of ★.1, and how to express in words what sound quality appeals to me after repeated listening. I finally came up with the metaphors of a silk scarf and an Imabari towel, which I think will help you understand!

Reversing all six key words shown in ★.1 may cause misunderstandings, so I will put a stop to it by quoting the following passage.

I think it's important to keep in mind that the seductive adjective "good-sounding" requires the proviso "moderate”.

If I were to elaborate on the word "moderate," I would suggest one indicator from the standpoint of my having listened to many components; namely, it is the way of looking at all components in unison, from entrance to exit, in terms of their structure and materials.

This idea of "moderate" is important. I have already mentioned that their design policy of using wood for the base and body of the amplifier is different from my own point of view. The fact that the tip of SPEC's wooden foot has a rounded, single point ground contact, or gentle spike shape, can be applied to the above idea of "moderate".

★.3 "There is a soft side to the hard, and an ambiguity that must be tolerated in the face of precision.“

However, the sound I'm experiencing here was made possible only by the SPEC RPA-MG1 power amplifier. Furthermore, by using the H-VC1000 volume control unit, the analog signal output from the DAC is sent directly to the RPA-MG1 without using a preamp, thus expressing SPEC's policy as a crystal-clear sound!

Now, 12 seconds after the start, Taeko Onuki's vocals come in.

"What? What's this voice? It's so soft and gentle, yet so clear. I can almost see her mouth!"

I was mesmerized by the quality of her voice! It is a musical texture that I had never known, even with my long experience! I still think silk scarves and Imabari towels are an appropriate metaphor, yet do not capture the essence.

The vocals were especially clear, but I experienced for the first time the moisture and smoothness that came from them, and above all, the temperature that I could feel with my ears!

One of the major beverage manufacturers has a catchphrase for its products, “Feels good going down on your throat”. I wonder if you can understand this nuance better if I say, "Feels fabulous passing through your ear“, or something like that.

I could never imagine that there is such a pleasant sensation brought about by Taeko Onuki's vocals in my ears.

What is it about SPEC that makes it so clear and warm at the same time?
Once again, my thought process was occupied with the search for the cause!

“I can certainly find the benefits of mechanical grounding, but when dealing with mechanical earth, how should I think about its placement and floor?”

It is important to know what the spikes will be driven into, for a component or a speaker equipped with metal spikes.

In my experience, the sound quality of the same speaker equipped with spikes varies greatly, when placed on a wooden floor versus a concrete or stone floor. 

Similarly, when storing amplifiers and players with spiked feet on a rack, the sound quality varies greatly depending on whether the shelves are made of wood or metal. 

This means that even if you apply mechanical grounding to an audio product with spikes, the sound quality will vary greatly depending on the installation.
Even if the product itself is designed based on the concept of mechanical grounding, the result will rely on the material and texture of the spike. 

That's why GOLDMUND even designed their own racks to adhere to their sound policy.
And I also have a specific preference for the racks we use on the floor of our store.


Now, let me reiterate what SPEC has done. "The tip of SPEC's wooden foot has a rounded, single point ground contact, or gentle spike shape." This is it!

Here's a little about my experience... When spiked speakers are placed directly on a concrete or stone floor, or in other words, when the spikes are placed directly against the floor, they do not produce a good sound. The highs will be harsh and high-pitched, and the lows will have a raised center of gravity. The same is true for power amplifiers and players. I think it is a mistake to think that they will not vibrate because they themselves are heavy, or they have their own weight.

When setting spikes on such a hard floor, it is important to use a wooden spike holder or base so that the metal spikes do not come in direct contact with the floor. Or, you can use a material that has the right amount of flexibility to convert vibration into heat.

Metal spikes and hard floors do not go well together, as shown by the story of two tons of concrete during the research and development of GOLDMUND. In other words, mass alone is not enough to counteract vibration, and isolation is necessary to counteract it.

Now that I've said all this, you might be able to know the true intention of SPEC.
"Is the amplifier a musical instrument? , “Did they use wood spikes to vibrate with the musical signal and produce a beautiful tone?”  No.  Not really!

I understood the purpose of SPEC's use of a wooden base chassis and insulators based on my own experience and listening to test tracks.

This means isolating audio equipment from improper locations, such as power supply areas where metal parts must be used, or places where major electrical components of the amplifier, such as circuit boards, are installed.

Again, even if we follow the mechanical grounding concept for the product itself, if the result depends on the material of the receiving side of the spike, we should fix it to the selected wood as the grounding target that we have to depend on in terms of sound quality.

Of course, this does not mean that maple, hickory, spruce, and other woods are perfect for isolation to control mechanical vibrations, and they are unlikely to make a sound.

I have already mentioned the principle that a speaker, as a transducer, uses the sound waves as a musical instrument, but I cannot accept the theory that the vibrations received by the base chassis and insulator of an amplifier beautify the musical signal.

Although I objected to SPEC's methodology for mechanical grounding at the beginning of this article, I believe that SPEC's wooden base chassis and floating grounding method have something in common in terms of philosophy, despite the differences in mechanical and electrical grounding. In a nutshell, it means "mechanical floating that does not depend on others.”

As I listened to a test track of Taeko Onuki that I've been using many times for the past 20 years, and heard her vocals which I'd never experienced before, I couldn't help but literally groan in admiration at the new possibilities that the SPEC RPA-MG1 brought to the table!  This is so good!  I'm not sure if SPEC had the same development intentions as I have stated above, though.(LOL)

As I have mentioned before, in this song, when the vocals come in, a deep reverb is applied, and a vast sound field is developed from the center-positioned mouth to the left and right spaces. Then, when the counter on the CD transport reaches 01:02, and the phrase, "Kazega tateba Kokoro Samuku, Hidamarino Fuyu (If the wind stands, it's cold at heart, winter in the sun)"ends, the reverb on the vocals disappears just as the Shinohara strings come in.

This is probably the mixing engineer's way of making sure that the reverberation of the strings in the background doesn't overlap with the reverb of the vocals, but you can clearly see Taeko Onuki's background sound change, like the scenery on a stage changing in an instant!

The idea of SPEC's wooden foot with a rounded tip and a single point of contact, or a gentle spike shape, was actually a similar design for the Ta.Qu.To-Zero spikes!

In other words, the semi-circular design, while functioning as a spike, prevents the vibration of the speaker itself from being reflected from the sharp spike tip by the hard floor.

That said, I don't know if SPEC used this experience and analysis to design the spikes that are the insulators of the amplifier. But the fact that it accurately reproduced the increase and decrease of reverb contained in the recording information made me very happy with the results!

Febian Reza Pane is a pianist who has participated in many of Taeko Onuki's songs, and his piano sounds extremely beautiful in this song as well.

Although his piano is only an accompaniment and does not assert itself strongly, I could clearly imagine the keys floating in the middle of the left and right speakers as well as the guitar and bass in the intro. The presence and lingering sense of his piano playing a moist melody made me want to say that the SPEC RPA-MG1 had really done it, with a feeling of sheer relief.

I was convinced that the spatial expression created by the sound of his piano was only possible because of the SPEC RPA-MG1's ability to clearly render the way the reverb was used as a background for the vocals. It's divine! It is absolutely beautiful!

In the final section, when the lyrics are about to end, two small instruments come into play. As I mentioned before, one of them is the bell that appears in the center. This bell is an instrument with many bells, called a handbell, as shown below.


This moment makes it all clear that the SPEC RPA-MG1 is equipped with this amazing feature of spatial expression performance that develops a wonderful sense of the sound field created in a studio, and produces the texture and timbre of musical sounds that other amplifiers cannot, just like I’ve mentioned earlier.

Was the number of bells increased?  Was reverb applied only to the handbells?
I can't hide my surprise at the cool, refreshing tone that brings those simple questions to mind!

Next is the claves, which are localized on the far right side. The sound of these claves is also different from what I remember!


This simple strumming sound can vary in a thousand ways depending on the speakers and system configuration. Because it is a very simple musical sound, it is easy to see how it can vary greatly, especially with speakers and amplifiers.

As mentioned in the previous example, the sound of the claves is a very beautiful extension of the lingering sound, but it is also reverbed. The very texture of the sound creation of that reverb effector will be noticeable.

Some amplifiers create a slightly noisy, squeaky reverberation, but the SPEC RPA-MG1 and Ta.Qu.To-Zero localize the sound in three-dimensional space, making you totally realize that it is purely a wooden instrument.

And the sound is precise enough to blend into the air with a gradual mitigation so long as you can actually measure the timeline of its disappearance with a stopwatch! This is incredible!  This is beautiful!  The genuine sound of the claves clearly shows the scent and the musical tone of the wood!

If you were to tell me that this is the amazing characteristic of the SPEC RPA-MG1 using a wooden chassis base, I would not be able to argue with you at all. The claves did sound convincing, hands-down!

Actually, I can't tell you how many times I have listened to Taeko Onuki's "Four Seasons" on the SPEC RPA-MG1!
Although it is a studio recording, and the music selection is excellent in terms of the musical texture and spatial expression, I'm not now interested in delving into the SPEC RPA-MG1 because it is a PWM class D amplifier.
Many magazine articles say that the PWM system has analog elements, but I evaluated the sound quality of the SPEC RPA-MG1 through the lens of my experience.

And even if the SPEC RPA-MG1 has an amplification circuit with common analog elements, I am confident that I can guess with a high degree of certainty that it would have the same tendencies and characteristics, even if a lot of wooden parts are used in the components of the amplifier that I have mentioned so far.

This is the first selection. One song alone contains all the musical sounds I need for my analysis - guitar, wood bass, various percussion, strings, piano, and vocals. The sounds are recorded in a very high quality way in this one piece.

The variety of those musical sounds saved me a great deal of time to analyze and evaluate the characteristics of the SPEC RPA-MG1.

What I have described so far can be demonstrated and proven at our store, and those characteristics can be felt as a common sound touchstone for all kinds of music.

Putting a similar analysis in writing on many of the songs I've enjoyed in this way can be a repetition of my impressions and a waste of the time I thought I had saved. The selection I used for this analysis is only one song, but of course I have listened to many others. I suppose this means that from that point on I enjoyed the music itself with the SPEC RPA-MG1!

I mentioned that Taeko Onuki's "Four Seasons" contained all the instruments I needed for my analysis, and it goes without saying that the exact same characteristics are confirmed in the other song selections as well.

As I have said many times before, all the actual conditions of the sound quality that I have evaluated can be demonstrated and proven in our store. This is a different kind of reliability from the evaluation in various media such as magazines, critics' articles, and the Internet. This is because here are the facts that can prove all of them!

To be honest, the RPA-MG1 was my first experience with SPEC amplifiers, and I can say from my analysis that their lower models have elements in common with the RPA-MG1.

Finally, I would like to conclude with a passage I wrote 26 years ago, "Misunderstanding by Unknown, Recognition by Experience.”

The sound of SPEC you experience in our store, H.A.L. will drastically change your conventional wisdom!

Author: Toshiaki Kawamata, Dynamic Audio Chief Director/Store Manager

In the Akihabara Electric Town of Tokyo, there is a long-established audio specialty store, Dynamic Audio, which has been in business for 56 years. Dynamic Audio has two stores: the main store "5555", which has a theme for each floor from the first to the seventh, and the "Trade Center", which consists of four floors.
Dynamic Audio is the leading audio specialty store in Japan, trusted by celebrities as well as people from all walks of life. The 7th floor of the main store "5555" especially, has carefully selected, top, high-end audio equipment, operated by Mr. Kawamata, the managing director and store manager. He is a convincing and trustworthy advisor and also known as a “sound doctor”, who has been delivering his evaluation of audio products to customers for many years. He posted his evaluation of SPEC's power amplifier RPA-MG1 (RPA-MG1000 for overseas markets) and control center MGC on his blog. He presents product introductions with his refined sensibility In H.A.L.'s Brief News, in December 2019 and June 2021. Here, let us share some of them with you.